Field of the Invention
The present invention relates to electrical signal combiners and splitters, especially, but not exclusively, signal combiners and splitters for sharing signals between two different wireless systems at a wireless base station.
Description of the Related Art
Modern wireless base stations often use one or more three-port antenna line devices (such as low-loss combiners, same-band combiners, filter combiners, or hybrid combiners), in order (i) to share received (RX) signals from two diversity antennas between two different wireless systems operating in the same site, and also (ii) to provide a path for signals to be transmitted (a.k.a. TX signals). See, e.g., U.S. Patent Publication Nos. US 2013/0162374 A1; US 2013/0077540 A1; US 2012/0249263 A1; US 2011/0051628 A1; US 2008/0174385 A1; US 2008/0169878 A1; U.S. Pat. No. 8,305,941 B2; PCT International Publication No. PCT/US2005/029858; and European Patent Publication Nos. EP 1243147 B1; EP 1096818 A1; and EP 0715786 B1, the disclosures of which references are hereby incorporated by reference. Prior-art combiners, however, tend to be relatively large and expensive and to have high insertion and return losses.